Preparation of peracetic acid



ed States atcn O lC 25,057 PREPARATION OF PERACETIC ACID Harold B. Stevens, Shawinigan, Quebec, Canada, assignor to Shawlnigan Chemicals Limited, Montreal, Quebec,

Canada, a corporation of Canada No Drawing. Original No. 2,830,080, dated Apr. 8, 1958, Ser. No. 581,383, Apr. 30, 1956- Application for reissue Feb. 18, 1959, Ser. No. 794,216

11 Claims. (Cl. 260-502) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to the preparation of peracetic acid, and in particular to the preparation by the catalytic oxidation of acetaldehyde.

The oxidation of liquid aeetaldehyde with gaseous oxygen, in pure or dilute form such as air oroxygen-enriched air, has been practised for many yea-rs. principal product of the oxidation was acetic acid. It was subsequently observed that acetic anhydride and water also are formed during the oxidation of liquid acetaldehyde with gaseous oxygen, and that acetic anhydride can be isolated from the oxidation mixture, giving acetic anhydride as the principal product.

It has also previously been observed that, during the oxidation of liquid acetaldehyde with oxygen gas, some peracetic acid can be formed. However, when acetic acid and acetic anhydride were sought as the principal prodacts, the accumulation of peracetic acid was undesirable, and conditions of reaction were always chosen to minimice or preclude the accumulation of peracetic acid. Peracetic acid, being an unstable and highly reactive compound, tends to decompose or further react under the conditions usually present in the oxidation of acetaldeexplosion.

It is now desired to produce peracetic acid in as high yield as possible by the oxidation of acetaldehyde with gaseous oxygen. It has been found that liquid acetaldehyde can be oxidized with oxygen-containing gas in the presence of certain materials which promote the accumulation of peracetic acid, and that satisfactory conversion of the acetaldehyde to peracetic acid can be obtained. Throughout this specification and the appended claims, reference to oxidation with oxygen-containing gas is to include oxidation with pure oxygen gas and oxidation with gascontaining oxygen in dilute form, for example air and oxygen-enriched air. It has also been found that the catalytic reaction for conversion of acetaldehyde to peracetic acid according to this invention. can be assisted by suitable temperature control. As the temperature of reaction increases, the rate of formation of peracetic acid increases, but the rate of decomposition of the peracetic acid also increases and can become so rapid as to render preparation of peracetic acid impractical at higher temperatures. The peracetic acid is formed in a reaction mixture from which it can, if necessary, be partially or completely separated, or in which it can be used directly, as a solution in diluent. The oxidationof acetaldehyde to peracetic acid can also be beneficially carried out in the presence of an organic liquid diluent.

The invention thus comprises a process for the preparation of peracetic acid comprising oxidizing liquid acetaldehyde with oxygen-containing gas in the presence of at least one halide salt catalyst of the group consisting of the chloride and bromide salts of copper, the chloride and bromide salts of cobalt, and cupric ammonium chloride. The process can be carried out either batchwise or as a continuous process as desired.

By the process of this invention, a reaction mixture.

Originally the i is produced which contains Re. 25,057 Reissued Oct. 17, 1961 satisfactory and useful proportions of peracetic acid; under normal conditions for the reaction, the process can achieve a peracetic acid yield of about 75% of the acetaldehyde oxidized.

Under preferred conditions, the oxidation of acetaldehyde to peracetic acid with gaseous oxygen is conducted at a temperature in the range between 0 and 50 C., most preferably between 5 C. and 40 C. However, the reaction can also be carried out at higher temperatures, for example up to 60 C., but the decomposition rate of peracetic acid at the higher temperatures is so high as to reduce the yield of peracetic acid to undesirably low levels. The reaction can also be carried out at lower temperatures, for example down to 30 C., but at the lower temperatures the reaction is undesirably slow and dehyde and helps reduce loss of acetaldehyde as vapor in any gases vented from the reaction. The presence of a liquid diluent also enables the reaction to be carried out with acetaldehyde in the liquid phase at temperatures above the latters boiling point at the prevailing pressure.

, Most desirable, however, is the effect of the liquid diluent in decreasing the extent of chemical reaction between peracetic acid and acetaldehyde, which reaction obviously has deleterious effects on the yield of recoverable peracetic acid. A particular advantage of the use of acetic acid as a diluent is that such diluent need not be completely separated from the reaction products to obtain a satisfactory commercial product, since acetic acid also is produced during the reaction and peracetic acid is usually sold as a solution in acetic acid solvent. The proportion of diluent maintained in the reaction mixture during oxidation is notcritical, and can conveniently vary between 0 and 90% by weight of the reaction mixture.

The proportion of catalyst required for the process of this invention can vary over the range of catalyst concentrations usually used in the oxidation of acetaldehyde with oxygen-containing gas, i.e., "usually in the range between 0.002% and 0.20% by weight of the reaction mixture.

It is possible and sometimes convenient to form a catalyst for the reaction of this invention in situ during reaction. This is readily done by introducing into the liquid reactant a soluble salt of, for example, copper or cobalt before starting the reaction, then introducing dry gaseous hydrogen chloride or hydrogen bromide to the reaction-with the gaseous oxygen, thus forming catalyst for the production of peracetic acid as oxidation proceeds. The refined product of the process of this invention is a solution of peracetic acid in acetic acid, the per-acetic acid constituting at least about 5% by weight of the acetic acid. The direct product of the process of the invention contains peracetic acid and acetic acid'but also includes catalyst residues, the diluent when liquid diluent has been used during oxidation, and also usually includes some unoxidized acetaldehyde. Concentrated peracetic acid can be separated from the reaction product by various methods, for example by low temperature distillations at very low pressures of the order of 1 to 10 millimeters A solution of peracetic acid in acetic acid can readily be obtained from'the direct product of the process of this invention by distillation at a pressure not greater'than about 40 millimeters of mercury.

Thefollowing examples are given to illustrate, but not to limit, the scope of the invention.

EXAMPLE 1 A. mixture of 60 gramso'f a solution of ethyl acetate containing about 0.01% y weight-cobaltous'cliloride hexahydrate and. '20 grams of acetaldehyde was charged to .a reactio-n vesseluconsisting of a vertical glass tube fitted with .a cooling jacket, a .sinteredglass difl'userlocated near the bottom to serve as the .gasinlet, a thermometer, a reflux condenser vented to the atmosphere,v

and means for. takingand returningliquor samples. The mixture .was cooled .to about .2 C. in. the reaction wesel; thenoxygenfrom a cylinder was added through the diffuser .at arate of two to three cubicfeet .per hour while the temperature of the reaction mixture was main.- tained. at about .5 .C.:3 C..by cooling. Sampleslwere drained from the reactionvessel periodically and analysedfor peracetic acidcontent. (Analysisfor peracetic acidwasbased on instantaneous liberationof icdineirom cold aqueousv potassium iodide solution acidified with sulphuric acid, :and immediate. titration of the iodinewith standard sodium thiosulphate solution.) The .acetaldehydecontent oefthe reaction mixture was also determined on thesesamplesby conventional means. A mixtureof onevolume ot-ethyl acetatecontaining 0.01% by weight of cobaltous chloride hexahydrate and .nine volumes .oli acetaldehyde wasslowly added to the. reaction -vessel at aratesuflicient to maintain thetotalvolume of liquor in the reaction vmsel approximately constant,-making up for the volumeof samplesn-emoved and the loss of volatilematerialaescaping-aswaponpast thetreflux-condenser. The

relative-proportions of ethyl acetateand acetaldehyde in this'rnixturewere chosen. in an-attempt tomaintain aesubstantially constantaconcentration. of ethyl acetate. intthe reaction vessel; Choice of thesuitable proportions was governed .by eificiency of the: reflux condensing .facil-- itiesifitted onthereactionsvessel. .A totalof .15 ml. of the foregoing mixture was: added to the reaction vessel over a period of one hour. hour after. theaddition of oxygen was started, the ;peracetic:acid content of reaction mixture had risen ted-9.5% byweight. The additionwof oxygen wasstopped about 20iminuteslater andrthe reactionmix cooled to? (3., sampled for analysis, and stored at 50 C. pendingdistillation. The

reaction=mixturewas found to. contain 18.5% by weight.

of peracetic acid. A sample of the reaction mixture-was thendistilled, in the absenceofzpermanentgases, by re.- peated evaporation at ,0. to 20-. and-condensation'at temperatures down to -'80' C. Thedistilled fraction richest in peracetic 'acidwas toimid to contain 31% 'by weight-of peraeetie acid .by the. analysis :proccdure outlined above. The presence ;of peracetic acid :in 1 this ,fraction in approximately this concentration "wasicommed by comparison of the: infrared spectrum oh its the ultraviolet spectrmrr of' axlsolution of the-:frarztion.

ants, and provided a more nearly constant overflow rate.

Portions of powdered solid catalyst were added to the vessel at intervals through a funnel, and were washed into the vessel with 5 ml. portions of ethyl acetate.

To star t,-.a slow stream-of nitrogenwas forcedthrough the difiuser, and 0.04 gram cobaltous chloride hexahydrate and 800 grams of 'a .mixture: of 9.0% ethyl acetate and 10% acetaldehyde :by weight -were charged to the vessel.. "The-i-temperaturecf the mixture-was adjusted to 20* C. a stream of 2- to 3=cubic=feet 'per'hour-of oxygen was substituted fortithenitrogen stream; Oxidation of the acct-aldehyde started, and the temperature of thereaction mixture was allowed torise -to3.5 C. and then maintained constant by cooling.., Ten minutes after the oxygemflow was-started, continuousaddition to the reaction vessel of a liquid feed mix containing 101% by weight of acetaldehyde and 90% by weight ofethylaee tate at a-rate of 600' to 700 perhour .was started. Solid cobal'tous ch-loi'idehexahyd'rate-was added to the reaction vessel in 0.02 gram portions. at intervalsof fifteen minutes. Periodic samples of they reaction mixture were analysed, andswhen the reaction mixture had. achieved a dynamic equilibriumcomposition, it wasfouml to. con' tain about7.% by weight-of peracetic acid, l.0l.5.% acetaldehyde, and about 2% acetic acid, the remainder being largely ethyl acetate. This dynamic equilibriun'i composition of reaction mixture was maintained without substantialvariation fora ,periodof four hours,'during which time about 235 grams .of acetaldehy admixed with ethyl acetate as indicated, was. added to the reaction mixture.

EXAMPLE. 3.

;A mixture of 40- grams .of acetaldehyde and 40 grams oflethylacetatesatmatedat room temperatm e'with cupric .bromideawas. charged :to the-=reaction-vessel used in Example .1.. mixture was-cooledto' 10 C.; then oxygenfromzaicylinder was added through "the" diifuser aha-rate; ofitwoutozthree-cubic' feet per hour while the temperatmeewas maintained at 10 by cooling. Periodic samples of the reaction mixture were analysed as inExarnple 1. The-volume of -liquid inthe reaction'vessel .was maintained constant by addition of acetaldehyde ethylzacetatermixtm'e containing nine volumes-of acetaldehyde to: one volumeof ethyl acetate saturated with cupricbromide. One and a quarter hours after oxidation..with-.oxygenhad started; the'penaeetic acid content ofzthereaction mixture=was found tobe--l6.8'%-by*weight.

EXAMPLE 4 A mixture of 203 grams ofi'acetaldhyde-andfiQgrams of ethyl" acetate saturated at room. -.temperalure..with

cobaltous' chloride hexahydrate .wasehargedl to the. re-

action 'vessel' used-in .Example 1.; The mixture cooled .to 10 Cj.;..then aamixture-of-oxygengas-from a cylinder. and. commercial nitrogen was added at arate ofittwo to three cubic feet pen .hour, while the temperature of :the reactiontm'ixturewasrheldat. 10' .C..;by cooling- .The liquid-volume inthe=reactien vessel was maintainedrconstant as in-Ex- .;l. Initially therproportion ofl oxygen in the "gas at about "22%" bywniume. One anrlgzat half-hours after=oxiizlatiou-started the reaction mixture was found to contain- -10.7% 'by "weight of peracetic acid. Atthe end of two-and a quarterhours theproportiomofiperacetieacid 'in the reaction mixture had droppedto 6;7%' 'by'weight' and'the proportion of mode acid "had 'increased, indicating'that. some ,of.the peracetic acid probably had been, converted to acetic acid; Then the proportion of oxygen .in the ;gas. .mixturebeiiig added wasgradually increased. .to 50% by a volume. At the endof-fourhoursfrom-thestart.ofthe tion of peracetic acid in the reaction mixture had risen to 14.0% by weight.

What is claimed is:

l. A process for the preparation of peracetic acid comprising oxidizing liquid acetaldehyde with oxygencontaining gas in the presence of at least one halide salt catalyst of the group consisting of the chloride and bromide salts of copper, the chloride and bromide salts of cobalt, and cupric ammonium chloride, to form peracetic acid.

2. A process as claimed in claim 1 in which oxygencontaining gas is pure oxygen gas.

3. A process as claimed in claim 2, in which the oxidation is carried out at a temperature in the range between '30 C. and 60 C.

4. A process as claimed in claim 3, in which the temperature is in the range between 5 C. and 40 C.

5. A process as claimed in claim 4, in which the oxidation is carried out in the presence of an organic liquid diluent.

6. A process as claimed in claim 5, in which the diluent is a liquid of the group consisting of methyl acetate, ethyl acetate, acetone, and acetic acid.

7. A process as claimed in claim 1, in which the oxygen-containing gas is air.

8. A process as claimed in claim 1, in which the oxygen-containing gas is oxygen-enriched air.

9. A process as claimed in claim 1, including the further step of separating the peracetic acid from the reaction mixture, together with a proportion of the acetic acid formed simultaneously with the peracetic acid, by distillation of the reaction mixture, to form a solution of peracetic acid in acetic acid.

10. A process as claimed in claim 1, in which the oxidation is carried out in the presence of liquid ethyl acetate as a diluent.

11. A process as claimed in claim 1, in which the oxidation is carried out in the presence of liquid methyl acetate as a diluent.

References Cited in the file of this patent or the original patent UNITED STATES PATENTS 1,179,421 Galitzenstein et a1. Apr. 18, 1916 FOREIGN PATENTS 272,738 Germany Apr. 6, 1914 730,116 Germany Mar. 19, 1943 OTHER REFERENCES Swern: Chem. Rev. :6 (1949). 

